I liked the way you implemented the special object and made the player have to use it in order to kill the elves.
The only problem I encountered while playing was this bug were if a bunch of elves were chasing me and I used the anvil, I'd kill one and the rest would stop moving and just freeze in place.
I understand that this was a submission for a week long game jam but, I feel you could have done more with your time and added more things to the game. Things I think you could have added are sound effects for when you kill an elf, decorations such as Christmas trees around the map to give the game more of a Christmas feel, making the player restart the game after an elf touches them. Small things like that to slightly improve the game.